DE 44 36 397 A1 relates to a device for aftertreating exhaust gases. It discloses a device for aftertreating the exhaust gases from a self-ignition internal combustion engine, in which, to improve the operation of a catalyst with a reducing action, a reducing agent is added to the exhaust gas fed to the catalyst. Here, the reducing agent is added by means of an electrically controlled dosing valve, which is combined in a common housing with a control valve. This control valve is used for the controlled introduction of compressed air supplied, in which a quantity of reducing agent supplied via the dosing valve is prepared and added intermittently to the exhaust gas. This serves, in particular, to avoid urea deposits and adhesions on the dosing valve and the control valve as well as to ensure optimum preparation of the reducing agent introduced.
DE 198 56 366 C1 relates to a device and to a method for aftertreating exhaust gases from an internal combustion engine operating with an excess of air. The proposal is for a device for aftertreating exhaust gases, said device comprising a reduction catalyst that serves to reduce NOx constituents in the exhaust gas. The device furthermore comprises an electrically controllable dosing device for the controlled introduction of reducing agent into an exhaust line upstream of the reduction catalyst and a device for cooling the dosing device. The dosing device comprises an injection valve, which is surrounded by a double-walled valve holder connected directly to the exhaust line. Moreover, the dosing device comprises a compressed air production device, which blows compressed air into an air gap between an outer wall and an inner wall of the valve holder in order to cool at least those parts of the injection valve which are close to the exhaust gas.
On its side facing away from the exhaust line, the valve holder has a recess matched to the diameter of the injection valve. This recess is bounded by the inner wall, with the result that, in the installed state of the injection valve, the outlet opening of the injection valve is situated just in front of or at the level of the wall provided with a through opening for the reducing agent to be introduced.
In the development of dosing modules (Advanced Dosing Module=ADM), an injection valve is included for the purpose of dosing urea. In order to position the valve tip of this dosing valve as close as possible to the exhaust gas stream, the valve receptacle in this dosing module is actively cooled. This is accomplished by way of a connection between the cooling member and the coolant circuit of the vehicle. This ensures that the temperature of the valve tip does not rise above 120° C., even when the dosing valve is positioned close to the exhaust gas.
One disadvantage of this embodiment is the absence of a cooling effect in the top region, i.e. in the region of the electrical contact means of the dosing valve. As a result, it is not possible to use this dosing module in ambient temperatures above 160° C. The electrical plug connection and the coil of the dosing valve are subject to damage at temperatures above 160° C., and therefore an outage of the valve and/or of the electrical contact means of the dosing valve may be expected.